This invention relates to a wave-shaping circuit applied in processing a digital signal.
Recently, progress has been made in the technique of processing digital signals. Analog signals such as audio signals are recorded after being converted into digital signals such as PCM signals. Also in the field of signal transmission digital signals are processed. In this connection it will be noted that reproduced or transmitted digital signals cease to have a perfect rectangular waveform, and instead are deteriorated due to the S/N ratio or frequency characteristic of a recording or transmission system. Therefore, it is necessary to carry out the wave-shaping of digital signals obtained in order to let the digital signals have the same rectangular waveform as the original signals. A wave-shaping circuit generally comprises a comparator for comparing the level of an input signal with a reference value and a holding circuit for reading an output signal from the comparator in response to a clock signal and holding the fetched signal.
Where, however, an input signal includes noises, then it sometimes happens that an output signal from the comparator ceases to denote a code corresponding to that of the original signal and is wave-shaped in the form of a wrong signal. A coding error is a detrimental problem in the processing of a digital signal. Further, the rectangular waveform of a digital signal has an extremely broad frequency spectrum. Consequently, the digital signals should have a broad frequency characteristic to assure proper recording and transmission, and be recorded or transmitted with greater density. However, the S/N ratio and frequency characteristic of the recording and transmission systems generally become less satisfactory in the higher frequency region. Where, therefore, digital signals are recorded or transmitted with higher density, then the percentage occurrence of errors tends to increase.